Method for determining magnesium and calcium activation rates of calcined phosphate tailings and application of method

Abstract

The invention relates to the technical field of solid waste reduction comprehensive utilization, in particular to a method for measuring the magnesium and calcium activation rate of calcined phosphate tailings and application thereof.The method comprises the steps that firstly, the phosphate tailings are calcined at the specific temperature, after the obtained calcined product is stirred with water and heated to be evaporated and crystallized, thermogravimetric analysis is conducted on generated sediment, and a weight loss curve is obtained; calculating the magnesium activation rate by comparing the weight loss ratio difference between the sample to be detected and the reference sample in the interval of 300-400 DEG C; and calculating the calcium activation rate by comparing the weight loss ratio difference in the range of 550-650 DEG C. According to the method, based on different decomposition temperatures of magnesium hydroxide and calcium hydroxide, interference of non-active components such as calcium carbonate and magnesium carbonate can be effectively eliminated, rapid, accurate and specific determination of the magnesium and calcium activation rate after calcination of the phosphate tailings is realized, and a reliable analysis means is provided for resource utilization of the phosphate tailings.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste reduction and comprehensive utilization, and particularly relates to a method for determining magnesium and calcium activation rates of phosphorus tailings after calcination and application thereof. BACKGROUND

[0002] With the continuous development of the phosphorus chemical industry and the continuous mining and selection of phosphate rock, the phosphate tailings in China are basically in a saturated or overloaded stacking operation state, and the original tailings have been unable to meet the needs of the continuous development of the phosphorus chemical industry, while occupying a large amount of land resources.

[0003] The main chemical components of the phosphorus tailings include Ca, Mg, Si, Fe, S, P, etc., wherein the content of CaO can reach 59.32%, the content of MgO is 15.45%, the main minerals are dolomite, apatite and quartz, and the content of dolomite is 83.40%, and the calcium and magnesium in the phosphorus tailings mainly exist in the form of dolomite.

[0004] The existing resource processing method of dolomite-based phosphorus tailings is mainly to prepare magnesium-based cementitious materials through calcination. When the phosphorus tailings are calcined to prepare magnesium-based cementitious materials, the magnesium component needs to be fully activated, and the calcium component needs to be activated as little as possible.

[0005] In the high-temperature calcination process of dolomite, the first stage is the decomposition of calcium magnesium carbonate at 700-900 DEG C, and the second stage is the decomposition of calcium carbonate at 900-1000 DEG C. In theory, there is a certain temperature difference in the process, but in the actual process, it is difficult to achieve the state of complete decomposition of magnesium and as little decomposition of calcium as possible, and it is difficult to measure. The method for measuring the activity of magnesium oxide in the industry cannot effectively exclude the interference of active calcium component. SUMMARY

[0006] The purpose of the present application is to provide a method for determining the magnesium and calcium activation rates of phosphorus tailings after calcination and application thereof, and to solve the problem that the existing method for determining the activity of magnesium oxide cannot effectively exclude the interference of active calcium component.

[0007] The scheme of the present application is as follows: A method for determining the magnesium and calcium activation rates of phosphorus tailings after calcination, comprising the following steps: S1, first calcine the first phosphorus tailings at a first temperature to obtain a first calcination product; add first water to the first calcination product, stir, heat and evaporate to crystallize to obtain a first precipitate; and perform thermal gravimetric analysis on the first precipitate to obtain a first weight loss curve; S2, performing second calcination on the second phosphorus tailings at a second temperature to obtain a second calcination product; adding second water to the second calcination product and stirring to evaporate and crystallize to obtain a second precipitate; performing thermogravimetric analysis on the second precipitate to obtain a second weight loss curve; S3, comparing the weight loss rate of the first weight loss curve at 300-400 DEG C with the weight loss rate of the second weight loss curve at 300-400 DEG C to obtain the magnesium activation rate of the second phosphorus tailings after calcination at the second temperature; comparing the weight loss rate of the first weight loss curve at 550-650 DEG C with the weight loss rate of the second weight loss curve at 550-650 DEG C to obtain the calcium activation rate of the second phosphorus tailings after calcination at the second temperature.

[0008] The decomposition temperature of magnesium hydroxide is 340-350 DEG C, the decomposition temperature of calcium hydroxide is 550-650 DEG C, the decomposition temperature of calcium magnesium carbonate is 700-900 DEG C, and the decomposition temperature of calcium carbonate is 900 DEG C, and the decomposition temperature difference of different components in the phosphorus tailings is used to evaluate the magnesium activation rate of the calcined phosphorus tailings under the interference of calcium oxide, magnesium oxide, calcium carbonate and magnesium carbonate.

[0009] As a preferred technical solution, the first phosphorus tailings and the second phosphorus tailings are the same batch of phosphorus tailings, and the chemical composition, content and mineral composition and content are the same.

[0010] As a preferred technical solution, the first phosphorus tailings are fully calcined to constant weight in the first calcination stage.

[0011] As a preferred technical solution, the first temperature in the S1 step is greater than or equal to 1000 DEG C, and the first calcination time is greater than or equal to 2h.

[0012] As a preferred technical solution, the first temperature in the S1 step is 1000-1200 DEG C, and the first calcination time is 2-4h.

[0013] As a preferred technical solution, the mass ratio of the first water to the first calcination product in the S1 step is first water: first calcination product greater than or equal to 10:1.

[0014] As a preferred technical solution, the mass ratio of the first water to the first calcination product in the S1 step is 10-20:1.

[0015] As a preferred technical solution, the second temperature of the second calcination in the S2 step is 700-900 DEG C, and the second calcination time is greater than or equal to 30min.

[0016] As a preferred technical solution, the mass ratio of the second water to the second calcination product in the S2 step is second water: second calcination product >= 10:1.

[0017] As a preferred technical solution, the mass ratio of the second water to the second calcination product in the S2 step is 10-20:1.

[0018] As a preferred technical solution, the ratio of the weight loss rate of the second weight loss curve at 300-400 DEG C to the weight loss rate of the first weight loss curve at 300-400 DEG C is the magnesium activation rate of the second phosphorus tailings; and the ratio of the weight loss rate of the second weight loss curve at 550-650 DEG C to the weight loss rate of the first weight loss curve at 550-650 DEG C is the calcium activation rate of the second phosphorus tailings.

[0019] As a preferred technical solution, the calcination temperature of the thermogravimetric analysis is >= 1000 DEG C, and the temperature rising rate is <= 10 DEG C / min, so that the same sample can obtain the same thermogravimetric analysis result under this thermogravimetric test system.

[0020] The application further discloses an application of a method for determining magnesium and calcium activation rates of phosphorus tailings after calcination in preparation of magnesium-based cementitious materials.

[0021] Advantages of the application: The method for determining magnesium and calcium activation rates of phosphorus tailings after calcination provided by the application mainly utilizes the principle that the decomposition temperatures of magnesium hydroxide and calcium hydroxide, which are the hydration products of magnesium oxide and calcium oxide, are different, the decomposition temperature of magnesium hydroxide is 340-350 DEG C, the decomposition temperature of calcium hydroxide is 550-650 DEG C, the decomposition temperature of calcium magnesium carbonate is 700-900 DEG C, and the decomposition temperature of calcium carbonate is 900 DEG C, so that the decomposition temperature difference of different components in the phosphorus tailings is utilized to evaluate the magnesium and calcium activation rates of the calcined phosphorus tailings under the common interference of calcium oxide, magnesium oxide, calcium carbonate and magnesium carbonate. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, purposes and effects realized by the application easy to understand, the application will be further described in combination with specific examples.

[0023] The embodiments of the application will be described in detail below with specific examples, but those skilled in the art will understand that the following examples are only used to illustrate the application and should not be regarded as limiting the scope of the application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0024] Example 1: A method for determining the activation rate of magnesium and calcium after calcination of phosphorus tailings, comprising the following steps: The selected phosphorus tailings for calcination test have the following main chemical components: calcium oxide (59.32%), magnesium oxide (15.45%), silicon dioxide (6.86%), and other elements, and the main mineral composition is dolomite (83.40%), apatite (11.21%), quartz (3.48%), and other minerals.

[0025] 100g of the phosphorus tailings (first phosphorus tailings) was weighed, calcined at 1100℃ for 3h to constant weight to obtain a first calcined product, 10 times the mass of water was added to the first calcined product for stirring, the stirring time was 1h, the stirred solution was heated and evaporated to constant weight to obtain a first precipitate, 1g of the sample was taken for thermogravimetric test, the thermogravimetric test system was calcination temperature 1100℃, and the heating rate was 8℃ / min, the weight loss rate of the first phosphorus tailings at 300-400℃ was 8.03%, and the weight loss rate at 550-650℃ was 7.32%.

[0026] In addition, 100g of the phosphorus tailings (second phosphorus tailings) was weighed, calcined at 800℃ for 1h to obtain a second calcined product, 10 times the mass of water was added to the second calcined product for stirring, the stirring time was 1h, the stirred solution was heated and evaporated to constant weight to obtain a second precipitate, 1g of the sample was taken for thermogravimetric test, the thermogravimetric test system was calcination temperature 1100℃, and the heating rate was 8℃ / min, the weight loss rate of the second phosphorus tailings at 300-400℃ was 5.33%, and the weight loss rate at 550-650℃ was 3.27%.

[0027] The activation rate of magnesium of the second phosphorus tailings calcined at 800℃ for 1h can be calculated as: 5.33÷8.03×100%=66.37%, and the activation rate of calcium is 3.27÷7.32×100%=44.67%.

[0028] Example 2: A method for determining the activation rate of magnesium and calcium after calcination of phosphorus tailings, comprising the following steps: The selected phosphorus tailings for calcination test have the following main chemical components: calcium oxide (59.32%), magnesium oxide (15.45%), silicon dioxide (6.86%), and other elements, and the main mineral composition is dolomite (83.40%), apatite (11.21%), quartz (3.48%), and other minerals.

[0029] Take 200g of phosphorus tailings (first phosphorus tailings), calcine at 1100℃ for 3h to constant weight, to obtain the first calcined product, add 10 times the mass of water to the first calcined product and stir for 1h, then heat and evaporate the stirred solution to constant weight to obtain the first precipitate. Take 1g of the sample for thermogravimetric testing, with a calcination temperature of 1100℃ and a heating rate of 8℃ / min. The weight loss rate of the first phosphorus tailings is 8.03% at 300-400℃ and 7.32% at 550-650℃.

[0030] Additionally, take 200g of phosphorus tailings (second phosphorus tailings), calcine at 700℃ for 30min to obtain the second calcined product. Add 10 times the mass of water to the second calcined product and stir for 1h. Then heat and evaporate the stirred solution to constant weight to obtain the second precipitate. Take 1g of the sample for thermogravimetric testing, with a calcination temperature of 1100℃ and a heating rate of 8℃ / min. The weight loss rate of the second phosphorus tailings is 5.24% at 300-400℃ and 1.58% at 550-650℃.

[0031] The activation rate of magnesium in the second phosphorus tailings calcined at 700℃ for 30min can be calculated as: 5.24÷8.03×100%=65.25%, and the activation rate of calcium is 1.58÷7.32×100%=21.58%.

[0032] Example 3: A method for determining the activation rate of magnesium and calcium in phosphorus tailings after calcination, comprising the following steps: Select phosphorus tailings for calcination test. The main chemical components of the phosphorus tailings are calcium oxide (59.32%), magnesium oxide (15.45%), silicon dioxide (6.86%), and other elements. The main mineral composition is dolomite (83.40%), apatite (11.21%), quartz (3.48%), and other minerals.

[0033] Take 50g of phosphorus tailings (first phosphorus tailings), calcine at 1200℃ for 2h to constant weight to obtain the first calcined product. Add 20 times the mass of water to the first calcined product and stir for 1h. Then heat and evaporate the stirred solution to constant weight to obtain the first precipitate. Take 1g of the sample for thermogravimetric testing, with a calcination temperature of 1100℃ and a heating rate of 8℃ / min. The weight loss rate of the first phosphorus tailings is 8.03% at 300-400℃ and 7.32% at 550-650℃.

[0034] Another 50g of the phosphorus tailings (second phosphorus tailings) is calcined at 900℃ for 2h to obtain a second calcined product, 20 times the mass of water is added to the second calcined product for stirring, the stirring time is 1h, the solution after stirring is heated and evaporated to constant weight to obtain a second precipitate, 1g of the sample is taken for thermogravimetric testing, the thermogravimetric testing system is calcination temperature 1100℃, the heating rate is 8℃ / min, the weight loss rate of the second phosphorus tailings at 300-400℃ is 8.03%, and the weight loss rate at 550-650℃ is 5.44%.

[0035] The activation rate of magnesium in the second phosphorus tailings calcined at 900℃ for 2h can be calculated as: 8.03÷8.03×100%=100%, and the activation rate of calcium is 5.44÷7.32×100%=74.31%.

[0036] Comparative Example 1 A method for determining the activation rate of magnesium and calcium in phosphorus tailings after calcination, comprising the following steps: Phosphorus tailings are selected for calcination test, the main chemical components of the phosphorus tailings are calcium oxide (59.32%), magnesium oxide (15.45%), silicon dioxide (6.86%), and other elements, and the main mineral components are dolomite (83.40%), apatite (11.21%), quartz (3.48%), and other minerals.

[0037] 50g of the phosphorus tailings (first phosphorus tailings) is calcined at 800℃ for 2h to constant weight to obtain a first calcined product, 10 times the mass of water is added to the first calcined product for stirring, the stirring time is 1h, the solution after stirring is heated and evaporated to constant weight to obtain a first precipitate, 1g of the sample is taken for thermogravimetric testing, the thermogravimetric testing system is calcination temperature 1100℃, the heating rate is 8℃ / min, the weight loss rate of the first phosphorus tailings at 300-400℃ is 5.12%, and the weight loss rate at 550-650℃ is 3.27%.

[0038] Another 50g of the phosphorus tailings (second phosphorus tailings) is calcined at 900℃ for 2h to obtain a second calcined product, 20 times the mass of water is added to the second calcined product for stirring, the stirring time is 1h, the solution after stirring is heated and evaporated to constant weight to obtain a second precipitate, 1g of the sample is taken for thermogravimetric testing, the thermogravimetric testing system is calcination temperature 1100℃, the heating rate is 8℃ / min, the weight loss rate of the second phosphorus tailings at 300-400℃ is 6.03%, and the weight loss rate at 550-650℃ is 4.34%.

[0039] The activation rate of magnesium in the second phosphorus tailings calcined at 900℃ for 2h can be calculated as: 6.03 ÷ 5.12 x 100% = 117.77%, the activation rate of calcium is 4.34 ÷ 3.27 x 100% = 132.72%.

[0040] Comparative Example 2: A method for determining the activation rate of magnesium and calcium of phosphorus tailings after calcination, comprising the following steps: The main chemical components of the phosphorus tailings selected for the calcination test are calcium oxide (59.32%), magnesium oxide (15.45%), silicon dioxide (6.86%), and other elements, and the main mineral composition is dolomite (83.40%), apatite (11.21%), quartz (3.48%), and other minerals.

[0041] 50g of the phosphorus tailings (first phosphorus tailings) was weighed and calcined at 1000℃ for 30min to obtain a first calcined product, 10 times the mass of water was added to the first calcined product for stirring, the stirring time was 1h, the stirred solution was heated and evaporated to constant weight to obtain a first precipitate, 1g of the sample was taken for thermogravimetric test, the system of the thermogravimetric test was calcination temperature 1100℃, heating rate 8℃ / min, the weight loss rate of the first phosphorus tailings at 300-400℃ was 7.12%, and the weight loss rate at 550-650℃ was 5.32%.

[0042] In addition, 50g of the phosphorus tailings (second phosphorus tailings) was weighed and calcined at 900℃ for 2h to obtain a second calcined product, 20 times the mass of water was added to the second calcined product for stirring, the stirring time was 1h, the stirred solution was heated and evaporated to constant weight to obtain a second precipitate, 1g of the sample was taken for thermogravimetric test, the system of the thermogravimetric test was calcination temperature 1100℃, heating rate 8℃ / min, the weight loss rate of the second phosphorus tailings at 300-400℃ was 8.03%, and the weight loss rate at 550-650℃ was 5.44%.

[0043] The activation rate of magnesium of the second phosphorus tailings calcined at 900℃ for 2h can be calculated as: 8.03 ÷ 7.12 x 100% = 112.78%, the activation rate of calcium is 5.44 ÷ 5.32 x 100% = 102.26%.

[0044] From the above examples and comparative examples, when the calcination temperature of the first phosphorus tailings is greater than or equal to 1000℃ and the holding time is greater than or equal to 2h, the activation rates of magnesium and calcium of the second phosphorus tailings calculated according to the scheme in the examples are within a reasonable range; when the calcination temperature of the first phosphorus tailings is too low or the holding time is too short, the activation rates of magnesium and calcium of the second phosphorus tailings calculated may be greater than 100%, which deviates greatly from the actual calcination activation rate.

[0045] Application Example: Preparation of phosphorous tailings-based cementitious material with optimized activation rate based on Example 1 In Example 1, it was calculated that the activation rate of magnesium was 66.37% and the activation rate of calcium was 44.67% after calcination at 800°C for 1h. This application example will demonstrate how to use this data to optimize the formulation of the cementitious material.

[0046] Application Steps: Determine the target amount of activity required: Assume that the theoretical formulation design of the target cementitious material requires 15g of “effective active MgO” and 10g of “effective active CaO” per 100g of cementitious system.

[0047] Calculate the amount of second calcination product required: According to the results of Example 1, calculate how much of the second calcination product obtained by calcination at 800°C for 1h needs to be weighed to provide the target amount of effective active components.

[0048] Calculate the amount of calcination product required to provide 15g of effective active MgO: Given that the activation rate of magnesium in the second calcination product is 66.37%, this means that 66.37% of the total MgO (15.45g) in the original phosphorous tailings is activated after calcination.

[0049] Therefore, the mass of effective active MgO per 100g of the second calcination product = MgO content in the original phosphorous tailings x activation rate of magnesium = 15.45g x 66.37% ≈ 10.25g.

[0050] Then, to provide 32.8g of effective active MgO, the required mass of the second calcination product = 32.8g / (10.25g / 100g) ≈ 320g. 32.8g of active MgO is not enough to complete the hydration reaction, so additional magnesium oxide is added, with 80g of 85 light-burned MgO, the mass of effective active MgO = magnesium oxide mass x magnesium oxide content x activation rate of magnesium = 80g x 85% x 60% = 40.80g.

[0051] Prepare the cementitious material and verify its performance: Weigh 320g of the second calcination product obtained by calcination at 800°C for 1h. Mix 80g of 85 magnesium oxide, a certain amount of (MgCl2 or MgSO4), and water by stirring. Pour the slurry into a mold and cure it to the specified age (7 days, 28 days). Measure its compressive strength. Compare it with the test results using different proportions of calcined tailings and 85 magnesium oxide.

[0052] Application Conclusion: As can be seen from the present application example, the magnesium and calcium activation rates determined in Example 1 provide key data support for the precise formulation design of the cementitious material. It makes it possible to: Quantitative feeding: upgrade from traditional "feeding according to total mass" to "feeding according to effective active components", realize the scientization and precision of the formulation.

[0053] Optimization of process: it is pointed out that under this formulation, the activation rate of magnesium is the limiting factor. If it is desired to reduce the cost, the amount of 85 light burned MgO needs to be reduced, if it is desired to take into account both the cost and the strength of the cementitious material, the amount of total active MgO needs to be considered comprehensively. The next step of process optimization should focus on how to reduce the activation rate of calcium (for example, try different calcination temperatures or times), so that the activation levels of the two elements are more matched, and the raw materials are used economically and efficiently.

[0054] Prediction of performance: the activation rate is directly related to the hydration reaction degree of the cementitious material, and is an important indicator for predicting its final mechanical performance.

[0055] The above shows and describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, the above examples and descriptions in the specification are only to illustrate the principles of the present application, without departing from the spirit and scope of the present application, the present application can have various changes and improvements, these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for determining the activation rate of magnesium and calcium after calcination of phosphorous tailings, characterized by, It comprises the following steps: S1, the first phosphorus tailings are calcined at a first temperature to obtain a first calcined product; the first calcined product is heated and evaporated by stirring with first water to obtain a first precipitate; The first precipitate is subjected to thermal gravimetric analysis to obtain a first weight loss curve; S2, the second phosphorus tailings are calcined at a second temperature to obtain a second calcined product; The second calcined product is heated and evaporated by stirring with second water to obtain a second precipitate; the second precipitate is subjected to thermal gravimetric analysis to obtain a second weight loss curve; S3, the weight loss rate of the first weight loss curve at 300-400℃ in step S1 is compared with the weight loss rate of the second weight loss curve at 300-400℃ in step S2 to obtain the magnesium activation rate of the second phosphorus tailings after calcination at the second temperature; the weight loss rate of the first weight loss curve at 550-650℃ is compared with the weight loss rate of the second weight loss curve at 550-650℃ to obtain the calcium activation rate of the second phosphorus tailings after calcination at the second temperature.

2. A method of determining the activation rate of magnesium and calcium after calcination of phosphorous tailings as claimed in claim 1, characterized by: The first phosphorus tailings and the second phosphorus tailings are the same batch of phosphorus tailings, and their chemical composition, content, and mineral composition and content are the same.

3. A method of determining the activation rate of magnesium and calcium after calcination of phosphorous tailings as claimed in claim 1, characterized by: The first phosphorus tailings are fully calcined to constant weight in the first calcination stage.

4. A method of determining the activation rate of magnesium and calcium after calcination of phosphorous tailings according to claim 1, characterized by: The first temperature in step S1 is ≥1000℃, and the first calcination time is ≥2h.

5. A method of determining the activation rate of magnesium and calcium after calcination of phosphorous tailings as claimed in claim 1, characterized by: The mass ratio of the first water to the first calcined product in step S1 is ≥10:

1.

6. A method of determining the activation rate of magnesium and calcium after calcination of phosphorous tailings according to claim 1 characterized in that: The second temperature of the second calcination in step S2 is 700-900℃, and the second calcination time is ≥30min.

7. A method of determining the activation rate of magnesium and calcium after calcination of phosphorous tailings as claimed in claim 1, characterized by: The mass ratio of the second water to the second calcined product in step S2 is ≥10:

1.

8. A method of determining the activation rate of magnesium and calcium after calcination of phosphorous tailings as claimed in claim 1, characterized by: The ratio of the weight loss rate of the second weight loss curve at 300-400℃ to the weight loss rate of the first weight loss curve at 300-400℃ in step S3 is the magnesium activation rate of the second phosphorus tailings; the ratio of the weight loss rate of the second weight loss curve at 550-650℃ to the weight loss rate of the first weight loss curve at 550-650℃ is the calcium activation rate of the second phosphorus tailings.

9. Use of the method for determining the magnesium and calcium activation rates of phosphorus tailings after calcination according to any one of claims 1-8 in the preparation of magnesium-based cementitious materials.

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